Preheat oven to 325 degrees.,In a saucepan, combine unsalted butter and brown sugar over medium heat.,Cook until it bubbles,stirring constantly.,remove from heat.,Lightly grease only the sides of a 10" round cake pan with 2" sides.,Pour about 1/3 of the topping into the pan.,Then cover the bottom with one layer of the pineapple slices.,Pour the remaining topping mixture over the pineapple.,Set aside.,In an electric mixer, combine flour, baking powder, salt, sugar, and butter until a uniform texture is achieved.,Add eggs one at a time, mixing after each addition.,Add sour cream and mix.,Add vanilla extract and mix for a couple minutes.,The batter will be pretty thick and fluffy.,Carefully spread batter over the pineapple and topping that you put in the bpttom for the cake pan earlier.,Leave 1/2 to 1/4 inch of space at the top, you may have some batter left over but don't overfill the cake pan.,______,Bake for 60-70 minutes or until a toothpick comes out clean from the center of the cake.,When the cake is done, remove it from the oven and get a cake platter or another cookie sheet to flip it out onto.,If you are going to use a cake platter, make sure there is room for the juices to flow out (at least 14" in diameter).,Place the top of the cookie sheet (or cake platter) over the top of the cake pan and quickly flip it over.,Then, gently lift the cake pan off, allowing the cake to fall out onto the cookie sheet.,Let the cake rest for 10 minuted before slicing into 12 pieces.,I recommend serving this cake with a scoop of vanilla ice cream.,Delicious!